Process for attachment of fibrous material to a backing



United States Patent 3,337,382 PROCESS FOR ATTACHMENT 0F FIBROUS MATERIAL TO A BACKlNG John Farago, Richmond, Va., assignor to E. i. du Pont de Nernours and Company, Wilmington, Del, 21 corporation of Delaware I No Drawing. Filed Nov. 23, 1962, Ser. No. 239,795

7 Claims. (Cl. 156310) This invention relates to an improved process for the attachment of fibrous materials to a backing and more particularly to a novel process for obtaining such attachments by chemical reaction between a layer of bonded fibrous material and a component of the backing.

A number of techniques are conventionally employed for securing backings to layers of a fibrous material. On a commercial scale the majority of these involve tufting and needle-punching operations or the use of adhesives. While the use of adhesive compositions would appear to be quite attractive for this purpose, in practice it is commonly found that such becomes prohibitive from the standpoint of economics since excessively large quantities of the adhesives are normally necessary to obtain a sufficiently strong physical bond between the backing and the fibrous material.

It is an object of this invention to provide a simplified process for attaching a backing to a layer of fibrous material. Another object is to provide a novel economic process for forming strong mechanical bonds between prebonded fibrous layers and a backing layer. A further object is to provide a processfor attaching a backing to bonded fibrous materials to form sutficiently strong bonds such that the backed fibrous articles may be washed, scoured, dyed, and the like without affecting the strength of the bond between backing and fibrous layer. An additional object is to provide a process which utilizes only minimum amounts of adhesive in forming a firmly adherent bond between a backing layer and a fibrous layer. Other objects will be apparent from a description of the invention given below.

According to the present invention, superimposed contacting layers of bonded fibrous material and backing material are adhered to one another by eifecting in situ polyesterification within the area of contact between complementary ester forming reactants contained in the respective layers. Thus one of the layers is so provided to contain a polyol reactant whereas the other is provided with a polymeric carboXylic reactant having either a plurality of extralinear carboxy radicals or ester forming derivatives thereof. The chemical reaction between the polyol and carboxylic reactants is readily effected by maintaining the two or more layers in substantially parallel and contacting arrangement while subjecting them to conditions to effect polyesterification, normally heat with or without a catalyst. As a result of the polyesterification, a secure weld is achieved between the layer of backing material and the layer of bonded fibrous material such that a highly useful unitary structure is produced.

In a preferred embodiment, the initial layer of bonded fibrous material to be employed is composed of a plurality of filamentary structures bonded in the form of a porous self-supporting material by means of a binder composition which comprises the polymeric carboxylic reactant. A particularly desirable class of polymeric carboxylic reactants which serve as the binder composition are those which contain, either in whole or in part, a homopolyrner or copolymer containing repeating units of acrylic acid, methacrylic acid or both. In conjunction with such a layer of fibrous material, a layer of backing material would then be used which contains a polyol reactant.

Typically suitable polyol reactants which can be used for carrying out the polycondensation reaction include ethylene glycol, glycerol, sorbitol, polyvinyl alcohol, sugars (e.g., glucose and sucrose), cellulose derivatives (e.g., cellulose, regenerated cellulose, cellulose acetate, ethyl cellulose), or any other monomeric or polymeric material containing a plurality of hydroxyl radicals per each molecule.

Representative polymers containing a plurality of carboxy radicals are polyacrylic acid, polymethacrylic acid, copolymers of acrylic acid and methacrylic acid, copolymers of either acrylic acid or methacrylic acid with one or more monomers such as the alkyl acrylates or alkyl methacrylates, and copolymers of maleic acid or fumaric acid with other monomers such as styrene or ethylene. It will be apparent that corresponding polymers can also be employed wherein a portion or all of the carboxy radicals are replaced by ester forming derivatives thereof, e.g., carbonyl chloride radicals, anhydrides and alkali metal and ammonium salts of the acids. Preferably the carboxylic reactants are normally solid polymers having a plurality, i.e., at least three extralinear carboxy radicals or derivatives per molecule of the polymer.

The layer of backing material can be composed of any suitable woven, knitted, or non-woven fabric such as burlap, a film such as polyethylene terephthalate film, polyethylene film, or polypropylene film, provided that such material is either composed of a plurality of free hydroXyl radicals or has been treated at least'on the surface with a compound to provide a plurality of hydroxyl radicals. One simplified form of the invention involves using as a layer of backing material a fabric composed essentially of cellulose derivative fibers which contain a plurality of reactive hydroxyl radicals. This obviates the necessity of using a separate compound containing the hydroxyl radicals which would otherwise have to be incorporated into the backing material as by coating or impregnation techniques.

The layer of fibrous material to be attached to the layer of backing material may be any conventional fibrous material such as woven, knitted, or non-woven fabrics, felts, non-woven batts, and the like. The filamentary structures, i.e., fibers, may be positioned in this layer in random fashion or they may be aligned in one or more preferential directions. Also the fibers may be bonded into a selfsupporting mass simply by means of the interconnections created during formation of the layer, e.g., by knitting, weaving, etc., or, as is preferred, by the use of a binder composition. In such a preferred embodiment, the layer of bonded fibrous material desirably comprises a porous self-supporting material as described in C. R. Koller, U.S. application, Ser. No. 787,662, filed Jan. 19, 1959, now U.S. Patent No. 3,085,922, i.e., one having a plurality of contorted, e.g., crimped, filamentary structures which overlap, are aligned generally in the same direction, are interconnected throughout the three dimensions of the material and the material has a fiber density below 25 lbs./ft. Although a description of these materials in cluding definitions of the terms used in connection therewith is set forth in the above Koller application, the dis closure of which is specifically incorporated herein by reference, they will be briefly mentioned herein. By contorted it is meant that the profile (i.e. side elevation) of an individual filament is irregular (i.e. not straight) when the filament is viewed from at least one side. In addition to being contorted, it is necessary that such filamentary structures overlap adjacent structures throughout the three dimensions of the article. By the term overlap is meant that in at least one view, a filamentary structure crosses over, with or Without touching or attachments, an adjacent filamentary structure. Furthermore it is critical to such structures that the contortion and overlapping of the filamentary structures do coact or are allowed to coact with one another. By coact is meant that the contortion and relative placement of the filamentary structures are such that they assist one another in producing and maintaining the claimed structures both with respect to the general alignment of the filamentary structures and their spacing with respect to each other to achieve the desirable densities contemplated. A bonded fibrous layer of such a material will be a porous, self-supporting sheet structure having two substantially parallel planar surfaces or faces, the planes of which would be intersected by the average direction of filament alignment by an angle of at least 30. The parallel planar surfaces will each be defined by cut filamentary ends, e.g., as created by slicing a porous body thereof traversely to the direction of filament alignment. Desirably the interconnections between filamentary structures of such a material are provided by a small amount of a binder composition.

The porous self-supporting materials as described in the aforementioned Koller application are particularly well adapted for use as the layer of fibrous material in accordance with the present invention. Primarily this is for the reason that the cut fiber ends defining one or both surfaces of the pile layer can be easily and permanently anchored to the backing material in upstanding condition without the use of excessive pressures and without embedding excesive quantities of the costly fiber. Furthermore, such materials can be readily provided which contain a carboxylic reactant as at least a portion of the binder composition.

In one embodiment a small amount of a binder composition is employed in the layer of fibrous material to provide a coating on the filaments to stiffen them and to connect adjacent filaments together at a number of crossing points along their lengths. Aside from the aforementioned polycarboxylic reactants, other binders can be used which are either soluble or insoluble, and either thermoplastic in nature or thermosetting. If it is desired to remove such a binder, a soluble variety will be employed which may be either organic-soluble or watersoluble. Suitable organic-soluble binders include natural rubber or synthetic elastomers (e.g., chloroprene, butadienestyrene copolymers, butadieneacrylonitrile copolymers), which may be used in the form of a latex dispersion or emulsion or in the form of a solution, vinyl acetate polymers and copolymers, cellulose nitrate, cellulose acetate, cellulose triacetate, polyester resins such as ethylene terephthalate/ ethylene isophthalate copolymers, polyurethanes such as the polymer from piperazine and ethylene bis-chloroformate, polyamide polymers, and copolymers, methoxymethyl polyamides, vinyl chloride polymers and copolymers such as vinyl chloride/vinylidene chloride copolymer latices. Alcohol soluble polyamide resins are also suitable organic-soluble binders. Suitable watersoluble binders include materials such as polyvinyl alcohol, sodium alginate, carboxymethyl cellulose, hydroxyethyl cellulose, dextrins, animal glue, soybean glue and sodium silicate. Suitable binders which are insoluble in organic solvents include polytetrafiuoroethylene and ureaformaldehyde resin latices.

Additional suitable binder compositions include chlorosulfonated polyethylene; butyl rubbers, such as isobutylene/isoprene copolymers; polyhydrocarbons, such as polyethylene, polypropylene and the like and copolymers thereof; high molecular weight polyethylene glycols sold under the trade name of Polyox; epoxide resins, such as the diepoxide of bisphenols and glycols; polystyrene; alkyd resins, such as polyesters of glycerol with phthalic or maleic acid; polyester resins such as from propylene glycol-maleic anhydride-styrene; phenolformaldehyde resins; resorcinolformaldehyde resins; polyvinyl acetals, such as polyvinyl butyral and polyvinyl formal; polyvinyl ethers, such as polyvinyl isobutyl ether; starch, zein, casein, gelatine, methyl cellulose, ethyl cellulose, polyvinyl fluoride, natural gums, polyisobutylene, shellac, terpene resins and rosin soaps. Segmented polymers, such as spandex polymers, polyether amides, polyether ured thanes (e.g., those in US. Pat. 2,929,800) and polyester/ urethanes are also suitable.

In the case of porous self-supporting layers of bonded fibrous material as described in the aforementioned Koller application and, as preferred for use herein, the initial body composed of a plurality of filamentary structures aligned in generally the same direction may be prepared from a wide variety of forms or fibers and filaments, such as, for example, continuous monofilaments, continuous multifilaments, carded webs, warp, sliver, top, roping, roving, tow, bulked tow, bulked continuous filament yarn, spun yarn, batts, felts, papers and other nonwoven webs, and the like. The fibers and filaments used as raw material may be either crimped or uncrimped, bulked or unbulked, drawn or undrawn or twisted or untwisted. The denier of the filaments is not critical and may vary from about 0.5 to about 50 denier or even higher.

The invention is broadly applicable to fibrous materials formed of polymeric materials of widely varying composition, both synthetic and naturally occurring. T ypical of the fibers and filaments which may be employed are those made of polyamides, such as poly(hexamethylene adipamide), poly(meta-phenylene isophthalamide), poly(hexamethylene sebacamide), polycaproamide, oopolyamides and irradiation grafted polyamides, polyesters and copolyesters such as condensation products of ethylene glycol with terephthalic acid, ethylene glycol with a /10 mixture of terephthalic/isophthalic acids, ethylene glycol with a 98/2 mixture of terephthalic/S- (sodium sulfo)isophthalic acids, and trans-p-hexahydroxylylene glycol with terephthalic acid, self-elongating ethyleneterephthalate polymers, polyacrylonitrile, copolymers of acrylonitrile with other monomers such as vinyl acetate, vinyl chloride, methyl acrylate, vinyl pyridine, sodium styrene sulfonate, terpolymers of acrylonitrile/ methylacrylate/sodium styrene sulfonate made in accordance with US. Patent 2,837,501, vinyl and vinylidene.

polymers copolymers, polycarbonates, polyacetals, polyethers, polyurethanes such as segmented polymers described in US. Patents 2,957,852 and 2,929,804, polyesteramides, .polysulfonamides, polyethylenes, polypropylenes, fluorinated and/or chlorinated ethylene polymers and copolymers (e.g., polytetrafiuoroethylene, polytritluorochloroethylenes) cellulose derivatives, such as cellulose acetate, celluose triacetate, composite filaments such as, for example, a sheath of polyamide around a core of polyester as described in U.S. Patent 3,038,236, and self-crimped composite filaments, such as two acrylonitrile polymers differing in ionizable group content cospun side by side as described in US. Patent 3,038,237, regenerated cellulose, cotton, wool, glass, metal, ceramic and the like. Blends of two or more synthetic or natural fibers may be used, as well as blends of synthetic and natural. Other fibers such as silk, animal fibers such as mohair, angora, vicuna are also suitable.

The liquid polyol reactants can be directly applied to a layer of either the backing material or fibrous material. Polyol reactants which are normally solid as well as polymeric carboxylic reactants can be applied to either of those layers from suitable solutions, dispersions or melts. It will be apparent that various additives may be included with either of the reactants or both, for example pigments, dyes, plasticizers catalysts, etc. Desirably both reactants are applied in a substantially uniform distribution to provide a continuous weld across the entire area defined by the contacting layers.

The polyol having reactive hydroxyl radicals can be contained in a binder serving to attach the fibers together in the layer of fibrous material, or it can be contained on the surface or throughout the backing layer Likewise, the reactive carboxyl radicals can comprise either the binder for the layer of fibrous material or may be contained within or on the backing layer.

After the layer of backing material has been brought in contact with the layer of bonded fibrous material, polyesterification is effected by known methods. This usually involves heating, normally to a temperature of at least 100 C., the area of the weld between the two layers such that esterification can occur between the hydroxyl radicals and either the carboxyl radicals or their derivatives. Often heating will be accompanied by the use of catalysts in order to speed up the polyesterification. Typical esterification catalysts which may be used in conjunction with the heat include sulfuric acid, Zinc chloride, paratoluenesulfonic acid, sodium hydrogen sulfate, and the like. The heat necessary to cause esterification can be applied to the backing only, for simplification of operation.

It is to be understood that the polyesterification reac tion involved in this invention will in a preferred embodiment, be a three-dimensional condensation reaction which involves chemical cross-linking. In this way the resulting bonds are thermoset polyesters which are stable to heating, washing, scouring, and other uses to which the final backed fibrous articles may be put.

The primary advantage afforded by the invention resides in the simplicity-of the method for providing a firmly adherent weld between the layers of fibrous material and backing. Significantly, this result can be achieved with substantial savings in material cost since only minimum amounts of adhesive forming reactants are required. Even further increases in such savings are made possible by the utilization of a binder composition for the fibrous material which also serves as the carboxylic reactant. Still another advantage of the invention involves confining polyesterification and the resulting formation of an adhesive to that area where the layer of fibrous material contacts the layer of backing material. Reactants which have not polymerized can thus easily be removed by an ordinary scouring step after the backed fibrous article has been prepared.

Although the invention has been particularly described with reference to the adhering of a single layer of fibrous material to a layer of backing material, it will be apparent that depending upon the intended use, two or more alternating layers of one or both materials can readily be united in a single operation.

The present invention may be used to prepare a wide variety of back fibrous articles, such as pile fabrics, floor coverings, such as carpets and tiles, furs, fleeces, blankets, apparel interliners, and the like.

The following example illustrates a specific embodiment of this invention without intending to limit the scope of the invention. All parts are by weight unless otherwise specified.

Example A strip of 12 x 36", 12 oz./yd. jute burlap backing material was brushed on one side with 5 oz./yd. of glycerol. A 12" x 36 porous sheet having a thickness of about A was employed as the layer of fibrous material. The sheet, produced in accordance with the above mentioned Koller US. application, consisted of a plurality of crimped polyamide fibers having a majority of the fibers aligned generally in the same direction. The two faces of the sheet were defined by cut filament ends, the two faces also being substantially perpendicular to the direction of filament alignment. Within the sheet the fibers overlapped one another, and also were attached to adjacent fibers at random intervals along their lengths by a binder composition of polyacrylic acid, the content thereof being 5% based on the weight of the fibers. The fibrous sheet and the burlap were placed between two fiat steel plates, one of which was electrically heated to 300 C. and the heated plate was brought into contact with the uncoated side of the jute burlap. Approximately 5 lbs/in. pressure was applied for 3 minutes. At the end of that time, the pressure was released and the burlap and fibrous sheet combination was removed from the heated zone. The burlap backing was .found to be adhered strongly to the fibrous sheet. Upon scouring with hot water the polyacrylic acid binder and excess glycerol was removed resulting in a soft pile fabric in which the pile was firmly anchored to the burlap. The force needed to pull a small group of polyamide fibers from the backing on the Instron tester was 5 pounds.

What is claimed is:

1. The method which comprises adhering superimposed contacting layers of bonded fibrous material and backing material by reacting a polyol reactant and a polymeric carboxylic reactant having a plurality of extralinear radicals selected from the group consisting of carboxy radicals and ester forming derivatives thereof, to effect in situ polyesterification within the area of contact between said polyol reactant and said polymeric carboxylic reactant, the reactant being contained in the said layer of bonded fibrous material consisting essentially of one of said reactants and the reactant being contained in the said layer of backing material consisting essentially of the other of said reactants.

2. The method of claim 1 wherein said layer of bonded fibrous material is a porous self-supporting material having a body formed of a plurality of lcontorted filamentary structures which are overlapping and are aligned in generally the same direction, said body constituting a network wherein at least a major proportion of the filamentary structures contact each other throughout the three dimensions of the body, the fiber density of the body being below 25 lbs./ft. said self-supo rting material having two substantially parallel planar surfaces, the planes of which would be intersected by the average direction of filament alignment by an angle of at least 30.

3. Method of claim 2 wherein said two substantially parallel planar surfaces are defined by cut filamentary ends and wherein said filamentary structures are interconnected by means of a binder composition.

4. The method of claim 3 wherein the binder composition is at least about 0.5% based on the weight of filamentary structures.

5. The method of claim 4 wherein said binder composition comprises said polymeric carboxylic reactant.

6. The method of claim 1 wherein said layer of bonded fibrous material contains as a binding agent said polymeric carboxylic reactant, said reactant having a plurality of repeating units of the formula c OH .wherein R is selected from the group consisting of hydrogen and methyl.

7. The method of claim 1 wherein said layer of backing material contains said polyol reactant.

References Cited EARL M. BERGERT, Primary Examiner.

J. P. MELOCHE, Assistant Examiner. 

1. THE METHOD WHICH COMPRISES ADHERING SUPERIMPOSED CONTACTING LAYERS OF BONDED FIBROUS MATERIAL AND BACKING MATERIAL BY REACTING A POLYOL REACTANT AND A POLYMERIC CARBOXYLIC REACTANT HAVING A PLURALITY OF EXTRALINEAR RADICALS SELECTED FROM THE GROUP CONSISTING OF CARBOXY RADICALS AND ESTER FORMING DERIVATIVES THEREOF, TO EFFECT IN SITU POLYESTERIFICATION WITHIN THE AREA OF CONTACT BETWEEN SAID POLYOL REACTANT AND SAID POLYMERIC CARBOXYLIC REACTANT, THE RACTANT BEING CONTAINED IN THE SAID LAYER OF BONDED FIBROUS MATERIAL CONSISTING ESSENTIALLY OF ONE OF SAID REACTANTS AND THE REACTANT BEING CONTAINED IN THE SAID LAYER OF BACKING MATERIAL CONSISTING ESSENTIALLY OF THE OTHER OF SAID REACTANTS. 